1. Technical Field
The present invention relates to a copy paper separating method for use in an electrophotographic copying apparatus which performs steps comprising forming a latent electrostatic image on a recording member, developing the latent image to a toner image, placing copy paper over the toner image on the recording member, charging the rear side of the copy paper to a polarity opposite to that of the toner by corona discharge to transfer the toner image from the recording member to the front side of the copy paper, and thereafter separating the copy paper from the recording member.
2. Prior art
Methods of separating the copy paper from the recording member heretofore known are divided into two general types: one in which a pawl, belt or like separating means (U.S. Pat. No. 3,450,402) is brought into contact with the recording member to forcibly separate the copy paper therefrom, and the other in which air is forced in between the leading end of the copy paper and the recording member, or the copy paper is subjected to suction on its rear side, or the charge on the rear side of the copy paper is erased by a.c. corona discharge, the methods of the latter type thus using separating means (U.S. Pat. No. 3,870,515) kept out of contact with the recording member for separating the copy paper.
Although the separating methods of the former type are advantageous over the latter in being much less prone to separation failures, the former methods have a drawback such that the separating pawl is likely to mar the surface of the recording member, or the use of the separating belt does not permit formation of a toner image on an end portion of the copy paper.
The latter methods are free of the above drawback. However, since the copy paper electrostatically attracted to the recording member is separated therefrom by a force applied to the paper to overcome the electrostatic attraction, separation difficulties or failures are liable to occur generally with variations in the ambient conditions (as when the ambient humidity is low) or variations in the properties of the copy paper (as when the copy paper is thin or has a high resistivity) which greatly alter the electrostatic attraction. Such failures may be reduced by subjecting the copy paper to an increased force of air or suction or to a.c. corona discharge at a higher voltage, but toner images of impaired quality will then result. Accordingly there is a limitation on the increase of the air or suction force, while the a.c. corona discharge method involves extreme difficulties in setting the discharge voltage.